A major problem in the world today is the contamination of materials, such as soil, by a wide variety of undesirable or toxic wastes. These wastes include various hydrocarbons including fossil fuels such as oil, gasoline, diesel, kerosene and the like, wastes from manufacturing, radioactive wastes, and biological contaminates. The cost of cleaning up these materials or sites runs into the billions of dollars.
Much of these wastes are currently being collected and then burned or encapsulated away from the site of contamination. These prior art methods are unsatisfactory in that they are expensive and cause their own contamination problems. For example, if the wastes are burned, they may not be burned completely and harmful byproducts may be released into the atmosphere. Encapsulation methods may alleviate the problem in the short term, but the wastes may continue to be released over time.
Excavation and disposal of contaminated soil in landfills is also becoming increasingly restricted by law. In some contaminated soil cases, such as contamination caused by tank leaks in urban or industrial areas, excavation is very expensive and sometimes even impossible without causing damage to surrounding structures. In situ treatment methods have distinct advantages over these methods in that they avoid extensive excavation costs and increase safety during treatment.
Existing in situ treatment methods involve heating soil with electromagnetic energy radiated from an antenna placed in a wellbore in the ground. Reliance on such thermal radiation wellbore techniques alone, however, is limited by 1) the cylindrical attenuation of the field power strength for each well, 2) exponential decay due to soil penetration depth, and 3) the use of extremely high energy electromagnetic radiation due to the ineffectiveness of ordinary radiation on hydrocarbons or non-polar contaminants. The resulting non-uniformity of soil heating causes limitations on well materials, overheating problems at particular wellbore sites, and poor application efficiency of the electromagnetic energy as well as very high cost and inherent dangers of generating high energy radiation. An example of in situ microwave radiation technology can be found in U.S. Pat. No. 5,370,477, the contents of which are hereby incorporated by reference.
A vacuum extraction method can also be used to remove contamination from the ground. This method, however, is only effective for a narrower range of contaminates than thermal treatment methods are, and it entails very long treatment times (up to years) which are difficult to predict, further complicated by variable weather. In this method, only contaminates with relatively high vapor pressures are removed. Low vapor pressure fractions of these materials are left behind. Materials such as diesel fuel, for example, constitute a variety of compounds with both high and low vapor pressures. Vacuum extraction, therefore, will unsatisfactorily selectively remove only the high vapor pressure fraction of contamination and leave behind high molecular weight, low vapor pressure materials.
What is needed is a composition and method of treating wastes more effectively and efficiently. Such compositions and methods should be capable of administration at the site of contamination. In addition, the compositions and methods should reduce the wastes to non-toxic products. Furthermore, the compositions and methods should be generally applicable to decontaminate a wide variety of wastes contained within a wide variety of carriers. The decontamination of wastes associated with a carrier, such as soil, should then render the carrier safe and reusable.
Accordingly, it is an object of the present invention to provide a composition and method for treating contaminated materials, such as soil.
It is further an object of the present invention to provide a composition and method for treating contaminated materials in situ.
It is further an object of the present invention to provide a composition and method for decomposing contaminated materials by subsequent exposure to radiation, such as microwave radiation.
It is further an object of the present invention to provide a composition and method for decomposing contaminated materials which renders associated carriers of the waste materials reusable.